title: Diffusion-weighted MR imaging of salivary glands with gustatory stimulation: comparison before and after radiotherapy.
abstract: BACKGROUND
  Xerostomia is the most prominent complication in patients with head and neck carcinoma after radiotherapy (RT). Diffusion-weighted magnetic resonance imaging (DWI) with gustatory stimulation may contribute to the evaluation of salivary gland function.
  
  
  OBJECTIVE
  To investigate the value of DWI for quantifying physiological changes of the parotid gland during gustatory stimulation in patients before and after RT.
  
  
  METHODS
  Magnetic resonance imaging (MRI) was performed in 28 consecutive patients with nasopharyngeal carcinoma before and after RT and clinical xerostomia was also assessed. A DWI sequence was performed once at rest and continually repeated seven times during stimulation with ascorbic acid. Apparent diffusion coefficient (ADC) maps for parotid glands at different time points and the range of increase with stimulation were calculated. Paired two-tailed Student t tests were used to compare the ADC values before and after stimulation, and before and after RT.
  
  
  RESULTS
  Before RT, the ADC showed an initial increase (P < 0.001) and then fluctuated during stimulation. After RT, as the clinical xerostomia changed from Grade 0 to Grade 2, the mean ADC at rest increased compared with the pre-RT value (P < 0.001). A similar response to stimulation was observed, but the range of increase between the maximum ADC during stimulation and the baseline value at rest was higher post-RT than pre-RT (P = 0.022). The minimum ADC during stimulation was higher than the baseline value post-RT (P = 0.028), but there was no difference pre-RT (P = 0.603).
  
  
  CONCLUSIONS
  DWI combined with gustatory stimulation seems to display the physiological changes of the parotid gland following RT and may be a potential tool for non-invasively assessing salivary gland function.
authors.affiliation: Department of Radiology, Fudan University Shanghai Cancer Center, Shanghai, PR China.
authors.forename: Yunyan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Dan
authors.initials: D
authors.lastname: Ou
authors.forename: Yajia
authors.initials: Y
authors.lastname: Gu
authors.forename: Xiayun
authors.initials: X
authors.lastname: He
authors.forename: Weijun
authors.initials: W
authors.lastname: Peng
authors.forename: Jian
authors.initials: J
authors.lastname: Mao
authors.forename: Lei
authors.initials: L
authors.lastname: Yue
authors.forename: Xigang
authors.initials: X
authors.lastname: Shen
mesh_terms: D000328:Adult; D000368:Aged; D001205:Ascorbic Acid / Q000008:administration & dosage; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D010306:Parotid Gland / Q000473:pathology* / Q000528:radiation effects*; D011446:Prospective Studies; D013649:Taste; D014987:Xerostomia / Q000175:diagnosis* / Q000473:pathology; D055815:Young Adult
chemical_list: D001205:Ascorbic Acid
keywords: Parotid gland; diffusion-weighted imaging; magnetic resonance; radiotherapy